Agaricus blazei Murill is originated from Piedate, a local area in Brasil, and is one kind of the mushrooms eaten in the area for a long time. In recent years, it has also been grown in Japan, and used as raw food and for medicinal purposes. Known efficacy of Agaricus blazei Murill includes enhancement and improvement of the liver, heart, stomach, intestines and the like, stabilization of blood pressure and blood glucose level, recovery of lumbago or neck stiffness, prevention of aging, improvement of immunity and the like. The efficacy attracting highest attention is an antitumor action (see patent document 1).
Researches utilizing the concept of amino acid imbalance proposed by Elvehjem in 1956 are ongoing on suppression of tumor growth by inhibiting protein synthesis in cancer tissues (see non-patent document 1). To be precise, attempts have been made to prevent growth of cancer cells by artificially creating a deficiency or excess state of a particular amino acid, and as one of such studies, amino acid imbalance preparations containing arginine in excess have been reported (see non-patent documents 2-4). It has also been reported that oral administration of arginine to Sarcoma-180 transplanted mouse affords marked antitumor effect and life extension (see non-patent document 5). Moreover, it is known that arginine, ornithine and citrulline constitute an in vivo ornithine cycle, and ornithine and citrulline are converted to arginine in the cycle.
In addition, a supplement for pet containing an extract of Agaricus or agaricus dried powder, and an amino acid is known (see patent document 2).    patent document 1: JP-A-10-316589    patent document 2: JP-A-2004-357507    non-patent document 1: “Fed. Proc.”, 1956, vol. 15, p 965    non-patent document 2: “Journal of New Remedies & Clinics”, 1977, vol. 26, No. 10, p 1877    non-patent document 3: “J Natl Def Med Coll”, 1982, vol. 7, No. 1, p 8    non-patent document 4: “J. Parent. Enter. Nutr.”, 1985, vol. 9, No. 4, p 428    non-patent document 5: “Exp. Animals”, 1973, vol. 22, No. 3, p 237-242